[Tex/LaTex] Does LaTeX automatically change fonts when switching between Title, Author, Date, and Body Text or sizes modifiers

fontsfontsizefontspecopentypetypography

I have a question regarding the inner workings of the system. Let us assume that I am using the article class.

I cannot help but notice that the title seems to have a different look than the body text—something about the curvature of the letters. (I could be mistaken, but it seems like simply switching sizes in Microsoft Word does not make the title look as nice as in LaTeX)

I know that when I downloaded Computer Modern Unicode, there are many *.otf files:

cmunbbx.otf
cmunbi.otf
cmunbl.otf
cmunbmo.otf
cmunbmr.otf
cmunbso.otf
cmunbsr.otf
cmunbtl.otf
cmunbto.otf
cmunbx.otf
cmunbxo.otf
cmunci.otf
cmunit.otf
cmunobi.otf
cmunobx.otf
cmunorm.otf
cmunoti.otf
cmunrb.otf
cmunrm.otf
cmunsi.otf
cmunsl.otf
cmunso.otf
cmunss.otf
cmunssdc.otf
cmunst.otf
cmunsx.otf
cmuntb.otf
cmunti.otf
cmuntt.otf
cmuntx.otf
cmunui.otf
cmunvi.otf
cmunvt.otf

So my question is, does LaTeX choose different otf files based on size or for title, author, date, and sections.

\title{}
\date{}
\author{}

\small{}
\large{}
\Large{}
etc.

Follow-up Question

Best Answer

that's called »optical sizes« or »grades«. A typeface designer may choose to draw several versions of a typeface, each optimized for printing at a certain size. For example, a grade optimized for printing at footnote size (say, 8pt) will usually have sturdier hairlines, less stroke contrast, maybe a bit looser spacing, maybe a decreased ascender-to-xheight ratio, probably less overall detail -- whereas a grade optimized for display use (say, size 24pt) will be more playful, have more contrast between vertical and horizontal strokes etc. The differences become most obvious when the different grades are scaled to the same absolute size.

click to enlarge

Nowadays, many fonts come in a ›Text‹ and a ›Display‹ version. Some have an additional ›Footnote‹ grade (or ›Caption‹, or ›Micro‹; there's no naming standards). But more than three grades are pretty rare. Donald Knuth drew eight of them for Computer Modern Roman Regular, five for CM Sans, four for CM Typewriter, only one for CMR Smallcaps etc. [although, see below, this wasn't adopted in the Unicode version].

In the days of letterpress printing, this practice was the norm rather than the exception. As (before the late 19th century) every fount had to be cut from scratch for a certain size anyway, a punchcutter would cut their 8pt punches not only smaller than their 24pt ones, but include other differences likes the ones above as well.

The overall aims of all this are (among others) to (1) improve readability at small sizes, (2) to prevent thin strokes from disappearing (or even parts of the metal punch breaking off) at small sizes, to (3) add variation, embellishments, detail etc. at large sizes (note, e.g. the loops in FF Clifford's italic Q or w), (4) to create a more uniform ›color‹ among the different sizes, as using the regular text grade in footnotes yields a color too light, and, for display, too dark.

Unless you are using Computer Modern Roman, TeX will only choose different fonts for different sizes if (1) you tell it to, and (2) you actually have a font that comes in different grades.

It's also possible to specify completely different fonts for the different sizes. I often use Playfair Display as a companion for Miller Text (as a cheapskate replacement for Miller Display). Using Xe/LuaTeX, fontspec's optical size feature can be used to that end:

\documentclass[12pt,DIV=7]{scrartcl}
\usepackage{fontspec,blindtext}
\setmainfont%
  [SizeFeatures={%
    {Size=-14,Font={Miller Text}},%
    {Size=14-,Font={Playfair Display}}}]{Miller Text}

\begin{document}
{\Large Lorem Ipsum \&c.}\par
\blindtext
\end{document}

enter image description here

PS: that said, the Unicode version of Computer Modern does not seem to come in different grades, as does traditional Latin Modern Roman. The reason the file list you posted is that long is simply that a lot of quite different fonts are part of the CM Unicode project. Knuth's sans, typewriter, typewriter proportional, upright (!) italic, etc., they're all in there.

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